unable to go to school

[MarthaSF321]

I've posted before about my DD year 9 who suffers from anxiety and panic attacks at school. She's under CAHMS and has just been referred to their clinical psychiatrist . CAHMS think she made need a EHCP with alternative provision for her education.
School have been supportive to a point but are now putting pressure on us to improve her attendance which is currently at 77%. I know that EHCP etc takes time. In the meantime I don't know how long the school will allow us to not send her to school as we have nothing diagnosed and no medical evidence just a verbal recommendation from CAMHS that school is the cause and she shouldn't go.
I will tell the school all this and keep her off, but I am reluctant to deregister her altogether as this will mean to chance of funding for alternatives.
What to do??